During perforating operations in a wellbore, the pressure response may be measured by one or more sensors immediately after the perforating guns have fired. The sensors are capable of recording pressure versus time at very high frequencies such that the pressure transient within a few milliseconds of the firing of the perforating guns is captured. For example, the sensors are capable of measuring at a rate of thousands or millions of pressure points per second. As a result, the sensors are oftentimes referred to as “fast gauges.”
The measured pressure response data is stored in a non-volatile memory and may be downloaded or read when the perforating gun is retrieved at the surface after the perforating operation is complete. The measured pressure response data may then be used to determine the quality of the perforations, the amount of perforation tunnel cleanup achieved immediately after the perforating guns have fired, and the like. If the data indicates that remedial actions should take place, the drill string may be run back into the wellbore again to perform the remedial actions. Thus, as may be appreciated, it would be beneficial to be able to transmit the data to the surface while the drill string remains in the wellbore.
Data may be transmitted up through a wellbore wirelessly using acoustic or electromagnetic signals. However, the data rates associated with such signals are oftentimes less than 100 bits/second or even less than 10 bits/second. These low data rates are inadequate to transmit the measured pressure response data to the surface in a reasonable amount of time. Furthermore, to transmit the entire data set would use large amounts of energy, which would quickly deplete the limited energy stored in the batteries in the wellbore. Data may also be transmitted up through the wellbore using a physical line or cable, however deployment of such a cable is not normally performed during perforating operations due to the added time, cost, and logistical complexities. Wired drill pipe or tubing may also be used to transmit data over a physical line but such techniques are not normally used during perforating operations due to logical considerations and a lack of availability of such hardware.